1. Field of the Invention
The present invention relates to a closed cycle type heat engine, particularly to a small-sized heating engine capable of effectively recovering a working medium gas.
2. Description of the Related art
A conventional closed cycle gas turbine of this type is disclosed in Japanese Patent Publication No. 59-51655. This gas turbine has a heater to effect a combustion air under pressure wherein the difference between the pressure of the working medium gas which cycles in the turbine (hereinafter referred to as cycle gas) at the heated side and the pressure of the combustion gas at the heating side is reduced, thereby heating the cycle gas at the high temperature. As a result, the temperature of the cycle gas is increased at the inlet of the gas turbine.
In a large scaled plant including the closed cycle type gas turbine, a compressor coaxially mounted on the turbine is driven to increase the pressure and the temperature for revolving the turbine. The reflux hot gas from the gas turbine is heat-exchanged in its heat and the temperature of the reflux gas is further decreased by a pre-cooler and supplied to a compressor where the pressure of the reflux gas is increased. Thereafter, the temperature of the reflux gas is increased. Consequently, the energy in the reflux gas is once lost which causes the problem in view of the thermal efficiency. Although the heat can be recovered by a different method in the more large scaled plant, the heat can be hardly recovered in the small scaled plant, thereby reducing the thermal efficiency.